The use of digital waveguide networks for digital signal processing and musical synthesis is disclosed in U.S. Pat. No. 4,984,276, which teaches the use of digital processors having digital waveguide networks for digital reverberation and for synthesis of musical sounds such as those associated with reed and string instruments. U.S. Pat. No. 4,984,276 is hereby incorporated by reference. The present invention concerns a digital waveguide hammer filter, which is a time varying digital filter that models a piano hammer or felt mallet.
The digital waveguide hammer filter of the present invention was designed to be used in conjunction with a one-dimensional digital waveguide network modeling a string (e.g., a piano string) to produce physically correct hammer-string interactions, and to be used in conjunction with a two-dimensional digital waveguide network modeling a membrane (such as a drum's surface) to produce physically correct mallet-membrane interactions. The digital waveguide hammer filter, however, can be used in conjunction with virtually any digital waveguide network, regardless of what the digital waveguide network is being used to model.
While the interactions of felt covered hammers with piano strings and the like has been the subject of study for some time, most such work has modeled strings and piano hammers in a manner that did not lend itself to real time musical synthesis with the microprocessors and digital signal processors typically found in music synthesizers and desktop computers in 1994 (i.e., microprocessors and digital signal processors capable of 33 million to approximately 100 million 32-bit mathematical computations per second).
Digital signal waveguides provide a methodology for simulating the operation of acoustic musical instruments and other resonators in a very computationally efficient manner, allowing real time computation of acoustic frequency waveforms in a resonating system with fairly modest computational resources. Recently issued patents using digital signal waveguides to synthesize musical tones in a manner that relates to the striking of a string by a hammer includes U.S. Pat. Nos. 5,187,314 (Kunimoto), 5,229,536 (Kunimoto) and 5,241,127 (Kobayashi), all of which are assigned to Yamaha Corporation of Hamamatsu, Japan.